Internal machining of large hollow cylindrical workpieces



O Umted States Patent 1111 3,543,635

[72] Inventors Maso Galbnrini; [50] Field of Search 90/11, 14, I

Francesco Cotta Ramusino, Milan, Italy 17 l 15; 77/3; 82/2.4 [21] Appl.No. 677,980 [22] Filed Oct. 25, 1967 1 References CIted [45] PatentedDec. 1, 1970 UNITED STATES PATENTS Assignee INNOCENTI Swim Genmle 11,852,601 4/1932 Boyer 90/171 llpdustria MelallurglcaeMec-canica3,097,568 7/1963 Kampmeien. 77/3x Mllan, Italy 1 3,131,584 5/]964McFerren 77/3 Pnomy g. 3, 1967 3,200,671 8/1965 Porath 90/14x [2 1 l q5266sA/67 3,404,588 10/1968 Anger 77/3 I 1 Primary Examiner-GilWeidenfeld AttorneySughrue, Rothwell, Mion, Zinn & MacPeak [5 4]INTERNAL MACHINING 0F LARGE HOLLOW CYLINDRICAL WORKPIECES 1s Clams 12Drawmg Figs ABSTRACT: A large hollow cylindrical workpiece is [52] U.S.Cl 90/11; 77/3; machined internally by milling or reaming toolssupported on 90/14 a tubular member which is itself supported coaxiallywithin [51] Int. Cl B23c 3/00, the workpiece for axial movement androtation under control B23b 39/02 of a headstock connected to one end ofthe tubular member.

Patentfzci Dec. 1, 1970 Sheet 1 01 6 Patented Dec. 1, 1975 Sheet rP/zzr/////////// (Pf/II r// I mw VIEW 0 m @N A 3 II g 1 RN mm Sheet PatentclDec. 1, 1970 mm w 5 3 mm Patenfd Dec. 1, 1970 Sheet 5; of6

Patented Dec. 1, 1 970 35 Sheet 6 of6 INTERNAL'MACHINING OF LARGE HOLLOWCYLINDRICAL WORKPECES The invention relates to the machining oflarge-diameter hollow cylindrical workpieces.

The invention has particular application to the machining of large-sizecomponents for use in, for example, electrical power stations. Suchpower stations tend to employ increasingly powerful generating units,which, therefore, are increasingly large in size. Components of suchunits are difficult to machine, a particular problem being the internalmachining of stator casings which are mostly welded structure of tubularshape and which may reach over 15 meters in length with bores of up to 4meters.

A particular problem concerns the internal reaming of stator casings forsecuring positioning bars for magnetic stator circuits, and themachining on such bars of slotted keyways extending parallel to the axisof the casing for the attachment of magnetic laminations having portionsof dovetail shape.

Internal machining of such large size workpieces cannot be carried outon conventional machine tools.

The present invention affords a solution to those problems by providinga method of internally machining a large-diameter hollow cylindricalworkpiece in which the workpiece is supported with its axis horizontaland a machining tool is 'supported inside the workpiece on at least onetubular member which extends coaxially within the workpiece and isitself supported externally of the workpiece, for axial movement and/orrotation about its axis under control of a rotary headstock connected toone end of the tubular member.

The invention also provides a machining device attached to a rotatableheadstock having a horizontal axis of rotation, an object of theinvention being to permit reaming or milling of large size workpieceswith a high degree of accuracy.

Accordingly the machining device of the invention comprises a tubularmember adapted to extend coaxially within a large-diameter hollowcylindrical workpiece to be machined and provided at one end with meansfor connection to said headstock externallyof the workpiece, tool holdermeans mounted on the tubular member for supporting a tool in machiningengagement with the internal surface of the work piece, and at least onesupport in which the tubular member is supported for axial movementand/or rotation about its axis under control of the headstock.

The device according to the invention is simple and sturdy inconstruction, easy to assemble and convenient to use, so that a numberof machining operations, such as those referred to above, may be carriedout with a reduced number of workpiece handling operations.

Further characteristic features of the invention will be understood fromthe following detailed description, given by way of example only, withreference to the accompanying drawings, wherein:

FIG. 1 is an axial sectional view of a machining device according to oneembodiment of the invention;

FIG. 2 is a cross-sectional view on line 11-11 of FIG. 1;

FIG. 3 is a cross-sectional view on line III-III of FIG. 1;

FIG. 4 is a side elevational view of a reaming-milling machinecooperating with the device according to the invention;

FIG. 5 is a front elevation of the machine from the direction of arrow Vof FIG. 4;

FIG. 6 is a diagrammatical cross-sectional view of one support for thedevice;

FIG. 7 is an axial sectional view on line VII-VII of FIG. 6;

FIG. 8 is a part-sectional diagrammatical side view of a device of thekind shown in FIGS. 1 to 7 shown in use for internal reaming of aworkpiece;

FIG. 9 is a view similar to FIG. 8 showing a portion of the device inuse for internal milling of a workpiece;

FIG. 10 is a part sectional diagrammatical side view of a machiningdevice according to another embodiment of the invention, shown in usefor internally milling a workpiece;

i a double lever 32 pivoted at 33 to the end plate 28, and en- FIG. 11is a diagrammatical elevation in a direction parallel to the axis of aworkpiece of a milling unit for use on the device according to theinvention, and

FIG. 12 is an end view in a radially inward direction of the millingunit shown in FIG. 11.

The machining device according to the invention comprises one or morehollow tubular members adapted to be mounted coaxially within a hollowcylindrical workpiece.

In order to carry out internal reaming and/or milling operations on verylong hollow cylindrical workpieces such as stators, two tubular members1, 1' differing in diameter, with the smaller diameter member 1 fittedcoaxially into the end of the larger diameter member 1, are employed asshown in FIG. 1.

- Each tubular member 1 (1') comprises outer walls 2 (2) of polygonalcross section (FIGS. 2 and 3) and internal walls 3 (3) of circular crosssection spaced from the outer walls and connected thereto by radial andlongitudinal reinforcing rnembers 4 (4) and 5 (5'), respectively,disposed respectively in planes perpendicular to and planes containingthe axis of the respective tubular member 1 (1 The faces of the outerwalls 2 (2') are machined to form along each longitudinally extendingedge a slideway 2a (Z'a).

The interiors of the two tubular members 1 (1') are accessi ble tooperators.

The larger tubular member 1 carries at one end means for connection toheadstock of a reaming milling machine having a horizontal axis ofrotation, with which the machining device cooperates. At its other endthe larger tubular member 1 carries a connecter ring 6 connected to acircular plate 7 which is secured by axially extending bolts 9 to acorresponding connecter ring 8 carried by the smaller tubular member 1'.

The ring 6 of the larger tubular member 1 supports through theinterposition of a crossed roller bearing 10 a rotatable annular member11 provided with an internal ring gear 12 which meshes with a pinion l3driven by a motor 14 through a reduction gearbox 14a. The annular memberI1, which is rotatable about the common axis of the tubular members 1,1', supports at least one slide 15 which is radially movable by means ofdriving'screws l6 and which supports a respective tool holder carriage17 on which a reaming tool (not shown) may be mounted.

The reaming-milling machine with which the machining device cooperatesis shown at 18 in FIG. 8, and shown in further detail in FIGS. 4 and 5.The machine 18 comprises a body 19 slidably mounted on a verticalstandard 20 which is in turn horizontally movable along slideways 25provided on a machine bed 92.

The body 19 supports a rotatable headstock comprising a platform 26rotatably driven about its axis by a main motor 21. An auxiliary motor21a is provided for effecting positioning displacements of the headstockplatform 26 about its axis and also for effecting displacements of thebody 19 along the standard 20.

A counterbalancing support comprising cables 22 and an oleodynamicpiston and cylinder 23, 24 balances the weight of the body 19 and theheadstock platform 26.

The platform 26 is provided on its forward face with a transversediametrically extending ridge 27 engaging on, assembly a diametricallyextending slot 28a (FIG. 1) in an end plate plate 28 which is secured tothe adjacent end of the larger tubular member 1. The plate 28 is alinedwith the rotatable platform by means of a central axially extendingdowel 29, which is hydraulically operated and ensures a coaxialrelationship of the tubular member 1 and the platform 26. A plurality ofscrew threaded axially extending bolts 30 are carried by the plate 28and have enlarged heads which are engaged in T- shaped grooves 31 in theplatform. The bolts 30 are tensioned by locking devices comprising anassociation with each bolt 30 gaged at its end remote from the bolt 30by a radially movable wedge 34 which is movable by a fluid pressureactuator 35.

The tubular members 1, l are supported by a plurality of supports 36,all similar to one another in structure, one of which is shown in H68. 6and 7. Each support 36 comprises a cradle structure formed by a lowerwelded frame 37 and an upper welded frame 38 interconnected by screwthreaded bolts and defining a circular recess receiving an annularhearing member 39 freely rotatable in the cradle structure on ahydrostatic suspension system. The hydrostatic suspension systemcomprises a plurality of chambers 4t) and 41 in radially and axiallyfacing surfaces respectively of the cradle structure, said chambers 4h,41' being supplied with hydrostatic fluid under pressure from a source Sto provide radial and axial support respectively.

The annular bearing member 39 has an internal wall of polygonal crosssection matching the external shape of the respective tubular member l,l. The tubular member 1, l is slidable axially in the bearing member 3%and is guided by the respective slideways 2a, 2a. The tubular member ll,1' is supported by a system of pressure chambers 42 defined between thefacing surfaces of the bearing member 39 and the tubular member ll, Eland supplied with hydrostatic fluid at a controlled pressure.Consequently, each tubular member l, l is free to slide axially androtate within its support 36, in response to positioning movements ofthe rotatable headstock platform 26, that is, both rotation of thelatter about its axis and translational movement of the reaming-millingmachine it along the machine bed slideways 25.

The smaller tubular member 1, is formed with a plurality of lateralaccess openings 43 adapted to be closed by shaped removable covers 44which conform to the external shape of the tubular member.

A supervising and/or control position is installed near the saidopenings 43 and comprises a swing seat 45 for an operator equipped withlighting, operating and control means 75 as well as with a protectionfor the operator himself. The seat 45 is rotatable about the axis of thetubular member 1 and in upright position even during rotation of thetubular members i ll. Support 72 is secured to the tubular member 1 or 1and positions the operators seat 45 through the pivotal mounting 73. Theseat 45 and control means '75 are suspended in such a manner fromsupport 72 so that their center of gravity is beneath the axis of thetubular member l or i even when the operator is present. Thispositioning of the center of gravity maintains the seat 45 and controlmeans '75 in an upright position during rotation.

A milling unit 37 may be fitted to the rotatable annular member ll ofthe larger tubular member 1 instead of reaming tools, and is secured tothesaid member llll by means of a bell crank strap 46 (FIG. 9) mountedon a radially extending slideway 15a on which the strap 46 isadjustable. The unit 437 comprises, as shown in FIGS. l1 and 12, asupporting bedplate 438 formed with grooves 49 for engaging the radialslideway 15a. The bedplate 48 accommodates internally a driving motor 55and a reduction gearbox 54 shown in broken outline for simultaneousdrive of a set of three milling cutters Si, 52 and 53 rotatable aboutparallel radially extending axes and carried by a milling head 50 whichis rotatable about an axis coinciding with the axis 51in of the middlemilling cutter i.

Rotation of the milling head 50 about the axis 51a permits variation inthe position of the two outer milling cutters 52, 53 in order to adjustthe overall width of the region to be milled between a maximum width Aand a minimum width A, as shown in FIG. R2. The milling unit 47 is usedfor milling stator casing 56.

As shown in FIG. 33, the device according to the invention may beemployed for carrying out internal reaming of a large stator casing 5'6which is mounted on conventional cradles $9 on a support table 5'7adjacent a machine bed and rotatable about a vertical axis for properalinement of the workpiece and provided with bottom positioning andlocking rams 5&5. Any conventional means for rotating the supportingtable may be used such as conventional rails 76 support motor drivenrollers 77 to permit the support table 57 to be rotated and therebypermit workpieces to be placed onto the support table from variousangles. Two fixed supports 36, 36a are provided outwardly of both endsof the stator 56 for rotatably and slidably supporting the larger andsmaller tubular members ll, ll respectively. The smaller tubular memberll is additionally supported at its free end by a further support 36bmounted on wheels 61 and movable over a horizontal surface 59 with whichone of the fixed supports 36a is engaged through the interposition ofadjusting dowels 64).

With the device according to the invention the internal surface of astator casing 56, whatever its length, may be internally reamed, FIG. 8,and milled, FIG. 9, after machining in a known manner the two endportions 9t), 91 of the stator casing, placing the workpiece on thesupporting table 57 and alining it coaxially with the tubular members l,l, which are retracted during setting up and then extended coaxiallyinto the workpiece by movement of the headstock on the machine bed toallow machining to commence.

in order to machine stator casings 56 of smaller length, it will besufficient to employ a machining device comprising a smaller tubularmember 1 alone, as shown in FIG. lb, which is directly attached to therotatable headstock platform 26 of a milling-reaming machine 18 througha plate 2:3 similar to the plate 28 employed in the embodiment of FIGS.1 to 9. The tubular member 1' is supported by a pair of supports 36carranged outwardly of both ends of the stator casing 56' to be machined,the latter resting on a support table 57 which is rotatable about avertical axis and lockable by means of positioning rams 5%.

l The device of FIG. it) enables milling to be carried out by means ofmilling unit 47 supported by a strap 46 adjustable radially on aslideway 36a. Owing to the small size of the stator casing 56' reamingcan be effected only by providing tubular extensions directly on theheadstock platform 26.

It will be understood that many constructional details of the inventionmay be varied with respect to that specifically described withoutdeparting from the scope of this invention as defined in the appendedclaims.

We claim: 1. A method of internally machining a large-diameter hollowcylindrical workpiece comprising the steps of:

supporting the workpiece with its axis horizontal; providing at leastone tubular member having a closable opening which extends coaxiallywithin the workpiece and is itself supported externally of theworkpiece;

supporting a machining tool on the tubular member inside the workpiece;

connecting a rotary headstock to one end of the tubular member forrotating the tubular member and moving it axially as required;

attaching a pivotably mounted control means and seat inside the tubularmember adjacent the opening;

rotating the tubular member; and

counterrotatingthe control means and seat relative to the tubular memberto provide a relative stationary position for observing and controllingthe machining of the workpiece.

2. A machining device for machining a large-diameter hollow cylindricalworkpiece, said device comprising a tubular member adapted to extendsubstantially centrally within the cylindrical workpiece; a headstock;means for moving the headstock in an axial and rotational direction;means at one end of the tubular member for connection to the headstockexternally of the workpiece; tool holder means mounted on the tubularmember for supporting a tool in machining engagement with the internalsurface of the workpiece; at least one support for supporting thetubular member during axial and rotational movement; a central meansprovided within the tubular member for machining the workpiece and arotatable seat means for supporting an operator of the control meanswithin the tubular member in a stationary upright position duringrotation of the tubular means.

3. A machining device for machining a large-diameter hollow cylindricalworkpiece, said device comprising a tubular member adapted to extendsubstantially centrally within the cylindrical workpiece; a headstock;means for moving the headstock in an axial and rotational direction;means at one end of the tubular member for connection to the headstockexternally of the workpiece; tool holder means mounted on the tubularmember for supporting a tool in machining engagement with the internalsurface of the workpiece; at least one support for supporting thetubularmember during axial and rotational movement; the headstock has atransversely'extending ridge and the means for connecting the tubularmember to the rotatable headstock comprise a plate secured to thetubular member at said one end and having a transverse diametricallyextending slot adapted to make a driving connection with thetransversely extending ridge provided on the headstock, the plate isfurther provided with a plurality of axially extending bolts, respectivedouble levers pivoted to the plate and engaging the bolts atone end,respective wedge members engaging the other ends of the respectivelevers, and fluid pressure actuators connected to the respective wedgemembers and operative to cause translational movement thereof to tensionthe respective bolts through the respective levers.

4. A machining device for machining a large-diameter hollow cylindricalworkpiece, said device comprising a tubular member adapted to extendsubstantially centrally within the cylindrical workpiece; a headstock;means for moving the headstock in an axial and rotational direction;means at one end of the tubular member for connection to the headstockexternally of the workpiece; tool holder means mounted on the tubularmember for supporting a tool in machining engagement with the internalsurfaceof the workpiece; at least one support for supporting the tubularmember during axial and rotational movement; the tool holder meansfurther comprising an annular member rotatably mounted at the end of thetubular member remote from said one end, at least one radiallydisplaceable tool supporting slide, supported on the annular member anddriving means for rotating the annular member about the axis of thetubular member.

5. A device as claimed in claim 4 in which said driving means comprise amotor mounted on the tubular member, a toothed pinion drivinglyconnected to the motor, and an internal ring gear provided on theannular member and meshing with said pinion.

b. A machining device for machining a large-diameter hollow cylindricalworkpiece, said device comprising a tubular member adapted to extendsubstantially centrally within the cylindrical workpiece; a headstock;means for moving the headstock in an axial and rotational direction;means at one end of the tubular member for connection to the headstockexternally of the workpiece, tool holder means mounted on the tubularmember for supporting a tool in machining engagement with the internalsurface of the workpiece; at least one support for supporting thetubular member during axial and rotational movement; and another tubularmember of smaller diameter than the first tubular member capable ofsupporting tool holder means, mounted coaxially within the first tubularmember at the end thereof remote from the headstock end.

7. A machining device for machining a large-diameter hollow cylindricalworkpiece, said device comprising a tubular member adapted to extendsubstantially centrally within the cylindrical workpiece; a headstock;means for moving the headstock in an axial and rotational direction;means at one end of the tubular member for connection to the headstockexternally of the workpiece; tool holder means mounted on the tubularmember for supporting a tool in machining engagement with the internalsurface of the workpiece; at least one support for supporting thetubular member during axial and rotational movement; the tubular membercomprises an external metal wall of polygonal cross section, an internalmetal wall of circular cross section coaxial'with and spaced from theexternal wall, and radial and longitudinal reinforcing members disposedrespectively in planes perpendicular to and planes containing the axisof the tubular member, and interconnecting the external and internalwalls.

8. A device as claimed in claim 7 in which the outer polygonal-sectionwall has longitudinal edges provided with slideways adapted to cooperatewith said support to facilitate axial sliding movement of the tubularmember.

9. A device according to claim 2 in which said tubular member isprovided with means defining at least one lateral access opening havinga removable cover which conforms to the external shape of the tubularmember.

10. A device as claimed in claim 9 comprising a single tubular memberprovided with attachment means for a milling machine near said accessopening.

ll. A machining device for machining a large-diameter hollow cylindricalworkpiece, said device comprising a tubular member adapted to extendsubstantially centrally within the cylindrical workpiece; a headstock;means for moving the headstock in an axial and rotational direction;means at one end of the tubular member for connection to the headstockexternally of the workpiece; tool holder means mounted on the tubularmember for supporting a tool in machining engagement with the internalsurface of the workpiece; at least one support for supporting thetubular member during axial and rotational movement; the supportcomprises an annular bearing member, cradle structure, fluid pressuresuspension means supporting the bearing member from the structure andpermitting rotation of the bearing member about its axis, and furtherfluid pressure suspension means supporting the tubular member from thebearing member and permitting relative axial movement of the tubularmember.

12. A device as claimed in claim 11 in which the bearing member andcradle structure have both radially and axially facing surfaces, and thefluid pressure suspension means for supporting the bearing member fromthe cradle structure comprises means defining a plurality of pressurechambers between both the radially and axially facing surfaces of thebearing member and the cradle structure, and means supplying fluid underpressure to said chambers to support the bearing member both radiallyand axially.

13. A machining device for machining a large-diameter hollow cylindricalworkpiece, said device comprising a tubular member adapted to extendsubstantially centrally within the cylindrical workpiece; a headstock;means for moving the headstock in an axial and rotational direction;means at one end of the tubular member for connection to the headstockexternally of the workpiece; tool holder means mounted on the tubularmember for supporting a tool in machining engagement with the internalsurface of the workpiece; at least one fixed support for supporting thetubular member during axial and rotational movement; and one movablesupport which is provided with wheels and movable axially with the tubular member to follow axial displacements thereof.

14. A machining device for machining a large-diameter hollow cylindricalworkpiece; said device comprising a tubular member adapted to extendsubstantially centrally within the cylindrical workpiece; a headstock;means for moving the headstock in an axial and rotational direction;means at one end of the tubular member for connection to the headstockexternally of the workpiece; tool holder means mounted on the tubularmember for supporting a tool in machining engagem'ent with the internalsurface of the workpiece; at least one support for supporting thetubular member during axial and rotational movement; the tool holdermeans include radially movable slides, and a milling unit supported onthe slides, the milling unit comprising a milling head, a plurality ofmilling cutters rotatable about parallel axes in the head, and means forrotating the head about a radially extending axis to vary the width ofthe area milled by the cutters.

15. A device for machining a large-diameter hollow cylindricalworkpiece, the device comprising a machine bed, a headstock, means torotate the headstock and more it member for supporting a toolirimachining engagement with the internal surface of the workpiece, aseat for an operator located in the aperture of the tubular member,means mounting the seat to cause it to remain upright despite rotationof the tubular member, and at least one support holding the tubularmember against lateral movement permitting axial and rotational movementof the tubular member in response to axial and rotational movement ofthe headstock.

